feat(kebab-tui): p9-fb-24 task 3 — Ask PgUp/PgDn page scroll

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/kebab-tui/src/ask.rs

@@ -439,6 +439,24 @@ pub fn handle_key_ask(state: &mut App, key: KeyEvent) -> KeyOutcome {
             s.input.delete_after();
             KeyOutcome::Continue
         }
+        // p9-fb-24: PgUp / PgDn page-scroll the transcript by
+        // `pager::PAGE_STEP` rows. Mode-agnostic (physical keys, no
+        // typing ambiguity). Both flip `follow_tail` to false so the
+        // user pinning the view via paging doesn't get yanked back to
+        // the bottom on the next streamed token (same contract as
+        // `j` / `k` from p9-fb-22).
+        (KeyCode::PageDown, _) => {
+            let s = state.ask.as_mut().unwrap();
+            s.follow_tail = false;
+            s.scroll = s.scroll.saturating_add(crate::pager::PAGE_STEP);
+            KeyOutcome::Continue
+        }
+        (KeyCode::PageUp, _) => {
+            let s = state.ask.as_mut().unwrap();
+            s.follow_tail = false;
+            s.scroll = s.scroll.saturating_sub(crate::pager::PAGE_STEP);
+            KeyOutcome::Continue
+        }
         // Insert mode: every non-chord Char (incl. e/j/k) types into
         // input. CTRL/ALT chords stay reserved.
         (KeyCode::Char(c), m)

crates/kebab-tui/tests/ask.rs

@@ -784,6 +784,60 @@ fn ctrl_l_resets_follow_tail_in_ask() {
     assert!(app.ask.as_ref().unwrap().follow_tail);
 }
 
+/// p9-fb-24: PgDn advances Ask scroll by `PAGE_STEP` (= 10) and
+/// disengages follow-tail (matches `j` semantics — manual scroll =
+/// freeze).
+#[test]
+fn page_down_advances_scroll_and_freezes_follow_tail_in_ask() {
+    let mut app = fresh_app();
+    app.mode = kebab_tui::Mode::Normal;
+    let outcome = handle_key_ask(
+        &mut app,
+        KeyEvent::new(KeyCode::PageDown, KeyModifiers::NONE),
+    );
+    assert_eq!(outcome, KeyOutcome::Continue);
+    let s = app.ask.as_ref().unwrap();
+    assert_eq!(s.scroll, 10, "PgDn shifts scroll by PAGE_STEP");
+    assert!(!s.follow_tail, "PgDn freezes follow_tail like j/k");
+}
+
+/// p9-fb-24: PgUp rewinds Ask scroll by `PAGE_STEP` (saturating at 0)
+/// and disengages follow-tail.
+#[test]
+fn page_up_rewinds_scroll_saturating_and_freezes_follow_tail_in_ask() {
+    let mut app = fresh_app();
+    app.mode = kebab_tui::Mode::Normal;
+    app.ask.as_mut().unwrap().scroll = 25;
+    app.ask.as_mut().unwrap().follow_tail = true;
+    handle_key_ask(
+        &mut app,
+        KeyEvent::new(KeyCode::PageUp, KeyModifiers::NONE),
+    );
+    let s = app.ask.as_ref().unwrap();
+    assert_eq!(s.scroll, 15);
+    assert!(!s.follow_tail);
+    app.ask.as_mut().unwrap().scroll = 3;
+    handle_key_ask(
+        &mut app,
+        KeyEvent::new(KeyCode::PageUp, KeyModifiers::NONE),
+    );
+    assert_eq!(app.ask.as_ref().unwrap().scroll, 0);
+}
+
+/// p9-fb-24: PgUp / PgDn fire from BOTH Insert and Normal modes
+/// (physical keys, no typing ambiguity — same as Left/Right/Home/End
+/// from p9-fb-22).
+#[test]
+fn page_keys_fire_from_insert_mode_in_ask() {
+    let mut app = fresh_app();
+    app.mode = kebab_tui::Mode::Insert;
+    handle_key_ask(
+        &mut app,
+        KeyEvent::new(KeyCode::PageDown, KeyModifiers::NONE),
+    );
+    assert_eq!(app.ask.as_ref().unwrap().scroll, 10);
+}
+
 /// p9-fb-22 (issue #95): when follow_tail is on and the transcript
 /// has many lines, the rendered buffer's last visible line includes
 /// content from the tail of the answer (not the head).